백준 백트래킹 - 15651번 : N과 M (3)

https://www.acmicpc.net/problem/15651

15651번: N과 M (3)

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import java.io.*;
import java.util.*;
public class Main {
	static BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
	public static void main(String[] args) throws IOException{
		BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
		
		StringTokenizer st;
		st = new StringTokenizer(br.readLine());
		int n = Integer.parseInt(st.nextToken());
		int m = Integer.parseInt(st.nextToken());
		int[] a = new int[n];
		for(int i=0; i<n; i++){
		   a[i] = i+1;
		}
		br.close();
		for(int i=0; i<n; i++) {
			dfs(a,"",m,i);
		}
		bw.close();
    }
	public static void dfs(int[] a, String target, int m,int idx) throws IOException{
		target = target.concat(Integer.toString(a[idx]));
		
		if(target.length()==m) {
			print(target);
			return;
		}
		for(int i=0; i<a.length; i++) {
				dfs(a,target,m,i);
		}
	}
	 static void print(String a) throws IOException {
		for(int i=0; i<a.length(); i++) {
			bw.write(a.charAt(i)+ " ");
		}
		bw.write("\n");
	}
}

시간 초과가 나서 System.out.println()을 Bufferedwriter로 바꿨더니 통과되었다.